langchain-oss-primer

name	langchain-oss-primer
description	ALWAYS START HERE for any LangChain, Deep Agents, or LangGraph agent building project. Required starting point before choosing other skills or writing any code. Covers framework selection (LangChain vs LangGraph vs Deep Agents), agent archetypes, dependency setup, and which skills to load next based on your decisions.

**Always load this skill first.** This is the required starting point for any LangChain open source agent project — before choosing other skills, before writing code, before installing packages.

It answers three questions every project must resolve upfront:

1. Which framework? — LangChain, LangGraph, or Deep Agents
2. Which agent archetype? — maps your use case to the right API and patterns
3. What to install and which skills to load next

Load this skill first. Once you've decided on a framework and agent type, follow the "Next Skills" section at the bottom — it tells you exactly which skills to invoke next based on your choices.

---

Step 1 — Pick Your Framework

The three frameworks are layered, not competing. Each builds on the one below:

┌─────────────────────────────────────────┐
│              Deep Agents                │  ← batteries included
│   (planning, memory, skills, files)     │
├─────────────────────────────────────────┤
│               LangGraph                 │  ← custom orchestration
│    (nodes, edges, state, persistence)   │
├─────────────────────────────────────────┤
│               LangChain                 │  ← foundation
│      (models, tools, prompts, RAG)      │
└─────────────────────────────────────────┘

Answer these questions in order:

Question	Yes →	No →
User needs or wants planning, persistent memory, complex task management, long-running tasks, out-of-the-box file management, on-demand skills, or built-in middleware, subagents, easy expansion capabilities?

You can combine layers in the same project. The most common pattern: Deep Agents as the top-level orchestrator, with a compiled LangGraph graph registered as a specialized subagent. LangChain tools and chains are usable at every level. **Python** **TypeScript** LangChain agent — provider-agnostic starting point. ``` # requirements.txt langchain>=1.0,<2.0 langchain-core>=1.0,<2.0 langsmith>=0.3.0 Deep Agents project — provider-agnostic starting point. ``` # requirements.txt deepagents langchain>=1.0,<2.0 langchain-core>=1.0,<2.0 langsmith>=0.3.0 ```bash # LangSmith — always recommended for observability LANGSMITH_API_KEY= LANGSMITH_PROJECT= # optional, defaults to "default"